We describe two patients who had acute myocardial infarctions during episodes of Capnocytophaga canimorsus sepsis. C. canimorsus is associated with severe infection in patients who are immunocompromised; one of these patients had undergone splenectomy for Hodgkin's disease 11 years earlier, and the other consumed significant amounts of alcohol regularly. Both patients owned dogs that had licked them or produced minor skin wounds shortly before they became ill. Coronary angiographic findings were normal for both patients. The association of acute myocardial infarction and sepsis with a specific pathogen is unique. This finding suggests that endothelial damage and coronary thrombosis due to C. canimorsus sepsis is a possible mechanism of acute myocardial necrosis.